ATP(−Mg2+) alters solvent accessibility for regions of Msh2-Msh6. A, change in percent deuteration of individual peptides from Msh2-Msh6 at 250 μm ATP(−Mg2+) predicted to fill both nucleotide binding sites and Msh2-Msh6 at 30s (black) and 300s (green). Peptides measured in both samples are shown as black and green bars spanning over the indicated sequence on the x axis. Positive and negative y axis values indicate enhancement and protection from deuterium exchange, respectively, caused by addition of the ATP(−Mg2+). Regions of substantial change are boxed. B, change in percent deuteration of individual peptides from Msh2-Msh6 at 4 μm ATP(−Mg2+) predicted to only fill the Msh6 binding site and Msh2-Msh6 at 30s and 300s as shown in “A”. C, regions of solvent protection (blue) and increased solvent accessibility (red) upon 250 μm ATP(−Mg2+) addition are mapped onto the ribbon diagram of Msh2-Msh6 (left) and the Msh2-Msh6 dimeric nucleotide binding domains (right). D, regions of the nucleotide binding domains protected at the lower 4 μm ATP(−Mg2+) concentration are depicted at the bottom.